A router is a device that receives data packets from one or more ports connected to one or more networks, such as local area networks (LANs) and wide area networks (WANs), and forwards the data packets through output ports selected according to each packet's destination. Based on routing tables and routing protocols, routers read the network address from each received frame and decide how to send the frame, possibly assisted by information, such as traffic load, line costs, speed, line integrity, etc., to select a most expedient route.
Core routers are the “heart” of any network. Only internal, or “core” protocols are run through these machines. No access (client) or transit lines should directly connect to these routers. Examples of core routing protocols are BGP and EGP.
Edge routers are on the perimeter of the core routers. They are responsible for properly receiving and sending traffic to and from customers, peers and transit pipes. Typical routing protocols within the edge routers are, for example, OSPF, IGRP, RIP, IS-IS and others.
Switches are network devices that filter and forward packets between network segments. Switches operate at the data link layer (layer 2) of the OSI Reference Model and therefore support any packet protocol. Networks that use switches to join segments are called “switched Networks” or, in the case of Ethernet networks, “switched Ethernet LANs.”
The Internet Protocol (IP), specified in Internet Engineering Task Force (IETF) Request For Comments (RFC) 791, forms the single packet protocol which currently defines all Internet traffic and content. Destination and source addresses for all IP packets are 32-bit quantities, whose leading bytes can be used to hierarchically determine where on the Internet these addresses reside. Routers organize their own hierarchy, roughly, into a layer of routers within an Internet Service Provider (ISP) and its connected subscribers, and a layer which connects discrete ISPs. Routers on the first level of hierarchy exchange address and network reachability information amongst themselves using a class of routing protocols called Interior Gateway Protocols (IGPs).
Routers on the second level of hierarchy, connecting discrete top-level ISPs, use a different group of protocols called Exterior Gateway Protocols (EGPs).
IETF RFC 1058 defines the RIP and RIPv.2 protocols, which are IGPs, specifying a format and means for exchanging interior routing data. With RIP, routers periodically exchange entire tables. Because this is insufficient, RIP is gradually being replaced by a newer protocol called “Open Shortest Path First” (OSPF).
Border Gateway Protocol v4, or BGPv4, is an EGP that exchanges network reachability information with other BGP systems. This network reachability information includes information on the list of Autonomous Systems (ASs) that reachability information traverses. On connection start, BGP peers exchange complete copies of their routing tables, which can be quite large. However, only changes (deltas) are then exchanged, which makes long running BGP sessions more efficient than shorter ones.
There are currently thousands of network devices such as routers, switches, firewalls, servers, hubs and other network traffic processing devices on the Internet, each of which must be properly configured to deliver the desired service. Configuring a network device typically encompasses creating a “configuration file” formatted according to the manufacturer's specification. Configuration files typically have a syntax wherein some property or attribute is named, followed by values which control the behavior of the property. After a configuration file is created, it is downloaded or “pushed” to the device, which implements the configuration. Once a device is configured, however, a user can log on to the device to change one or more of the properties. Historically, these devices have been configured one at a time by operations personnel. Yet, service providers often roll out new services that are too complex and difficult to be configured manually.
The goal of network configuration management is to generate, deploy and track configurations and configuration changes for a potentially very large number of network software and hardware elements.
With traditional manual-configuration practices, the sheer volume of configuration work requires the participation of many different ISP operations personnel. Often these people use different methods and “recipes,” resulting in inconsistent device configurations across the network. This in turn can lead to poor service quality and even service outages.